Parking Lot Accident

[Spaceman]

My roommate got in a very minor parking lot accident last month. Apparently him and this girl were both backing out of their respective spaces and the two cars' bumpers slightly rubbed (his driver-side rear and her passenger-side rear bumper). His bumper came out without a single scratch, as in I can't even find the point of contact on his bumper. He has a photo that he took of the girl's car and there is an approximately 8" line on her bumper, stretching from the side to the rear of the bumper. I can't tell from the pic if it's a scratch or not but he says it wasn't and since there are no scratches on his car, I don't think hers could have been that bad.
On the scene he told the girl that they can settle this (he didn't want to report to his insurance) and they exchanged license # and names. He also says the other side of the girl's bumper was damaged and hanging pretty low from a prior accident. The girl called him last night and told him that she's gotten an estimate of $700 for the repair. He offered to pay $100 but she didn't accept.
I think the $700 is the estimate to fully repair the bumper, including the prior damages. Since I am not even sure that my roommate's at fault for the accident, I think he should just report it to his insurance and have the girl do the same and let the insurers work it out but I just want to know what you guys think about it before I tell him to do that. $700 seems outrageous for a single scratch that will most likely just buff out!!

[aardvarc]

You don't mention the state - but in the majority of states, for vehicle crashes on private property (ie parking lots), you're REQUIRED by state LAW to exchange driver's license, registration and INSURANCE information.

[Spaceman]

Sorry forgot the state: it was in CA. What happens when they don't exchange insurance info? At this point, is he better off paying the $700 or calling his insurance? I would have advised him to get a lawyer if it was a larger sum or if the accident involved injury.